The British yeomanry during the First World War were part of the British Army reserve Territorial Force. Initially, in 1914, there were fifty-seven regiments and fourteen mounted brigades. Soon after the declaration of war, second and third line regiments were formed. However, the third line regiments were soon absorbed into the Cavalry Reserve Regiments, to supply replacements for the cavalry and yeomanry. Other horsed regiments in the British Army, during the war, were the regular cavalry regiments and the three regiments belonging to the special reserve: the North Irish Horse, the South Irish Horse and the King Edward's Horse.[1] The senior yeomanry regiments could trace their origins back over 100 years; the oldest regiment, the Royal Wiltshire Yeomanry, had been formed in 1794. The most junior regiment, the Welsh Horse, had only been formed on 18 August 1914, after the start of the war.[2]
To expand the yeomanry, mirror regiments and brigades were formed. The Yorkshire Hussars part of the Yorkshire Mounted Brigade was numbered the 1/1st when the second regiment was raised, which became the 2/1st Yorkshire Hussars in the 2/1st Yorkshire Mounted Brigade and so on. Mounted brigades were often broken up or renumbered, the aforementioned 2/1st Yorkshire later became the 18th Mounted Brigade.[3] Although there were no yeomanry divisions before the war, after mobilisation, the mounted brigades were allocated to specially formed mounted divisions. Some regiments also served alongside regular cavalry regiments in cavalry brigades. While others were assigned to infantry divisions or army corps as their horsed regiment.
The yeomanry fought in several theatres of war. On the Western Front, they were initially used in their traditional role, but during the campaign in Gallipoli, the 2nd Mounted Division fought dismounted. Later, the yeomanry fought on the Macedonian front where, as part of the British Salonika Army, they were once again employed in the mounted role. Further mounted actions followed with the Egyptian Expeditionary Force in the Sinai and Palestine Campaign. Some yeomanry regiments had a mixed war with several being converted to cyclist units. Others became infantry battalions like the 1/1st Yorkshire Hussars, which ended the war as the 9th (Yorkshire Hussars Yeomanry) Battalion, West Yorkshire Regiment. Several regiments serving in the Middle East were converted to infantry and used to form the 74th (Yeomanry) Division, which then fought on in Palestine before being transferred to France. In 1918, other yeomanry regiments were transferred to the Western Front to form battalions of the Machine Gun Corps. By the end of the war, the yeomanry had suffered over 3,800 dead, which included several senior officers.